Enhancing the Intense Field Control of Molecular Fragmentation

We describe a pump-probe scheme with which the spatial asymmetry of dissociating molecular fragments—as controlled by the carrier-envelope phase of an intense few-cycle laser pulse—can be enhanced by an order of magnitude or more. We illustrate the scheme using extensive, full-dimensional calculations for dissociation of ${\mathrm{H}}_2^{+}$ and include the averaging necessary for comparison with experiment.

Figure 1

Vibrational state distribution before and after the 45 fs, ${10}^{13}\mathrm{W}/{\mathrm{cm}}^2$ pump pulse.

Figure 2

Franck-Condon-averaged $K^2\rho (\mathbf{K})$ (integrated over ${\phi }_K$) for probe-only [$\rho (\mathbf{K})$ is reflected to $-K_{\perp }$ for clarity] for (a) $\phi =0$, (b) $\phi =\pi /4$, (c) $\phi =\pi /2$, and (d) $\phi =3\pi /4$ (Gray dotted lines mark $K=7.5$, 10, 12.5, and 15 a.u.). (e)–(h) are same as (a)–(d) but for pump-probe. All cases used a 7 fs, ${10}^{14}\mathrm{W}/{\mathrm{cm}}^2$ probe pulse.

Figure 3

(a) Asymmetry defined in Eq. (5) for the probe-only case and (b) for the pump-probe case for a ${\tau }_{\mathrm{FWHM}}=7\mathrm{fs}$ and $I={10}^{14}\mathrm{W}/{\mathrm{cm}}^2$ pulse.

Figure 4

(a) Asymmetry from the intensity-averaged $\rho (E,\widehat{K})$ for the probe-only (thin dashed lines) and the pump-probe (thick dashed lines) cases as well as for a single 7 fs probe pulse with a peak intensity of $1.2\times {10}^{14}\mathrm{W}/{\mathrm{cm}}^2$ (thin and thick solid lines, respectively). (b) KER distributions for the cases shown in (a) normalized to the same peak value.